The reaction of octafluorotoluene with hexafluoropropene is known to make the perfluorinated iso-butylbenzene as shown below:
from “Syntesy Ftororganicheskich Soedinenii. Monomery I promezhutochnye porukty. Eds. I.Knunyants and G. Yakobson, Khimiay, Moskve, USSR, 1977, p. 141.